Apparatus for heat treating packaged products

ABSTRACT

A product tightly enclosed in a flexible package is subjected to heat treatment in a heat-inducing field while supported by a device comprising a plurality of flanges closely spaced from each other and lying close to the package so as to prevent its destruction due to internal pressure increase during the heat treatment. The flanges are positioned to expose the package over a large part of its surface, so that such part is accessible to a cooling medium.

Unite States Patent [191 Stenstrom APPARATUS FOR HEAT TREATING PACKAGED PRODUCTS [75-] Inventor: LenuartArvid Stenstrom,Huddinge,

Sweden [52] US. Cl. 269/287, 206/46 FR [51] Int. Cl B23q 3/00 [58] Field of Search 99/443 C; 126/41 C; 53/25, 127, 388; 219/388; 21/80, 105; 34/236, 237, 238; 107/57 R; 198/162, 198,

[56] v References Cited UNITED STATES PATENTS 3,280,969 10/1966 Evans et a1. 206/46 FR 3,476,235 11/1969 Mills et a1. 206/46 FR 3,144,979 '8/1964 Young 206/46 FR x 839,868 1/1907 Morey 198/162 X 2,036,643 4/1936 Richard 198/162 X 2,305,044 12/1942 Toews 198/198 3,044,608 7/1962 Bachleder et a1.. 206/46 FR 3,261,110 7/1966 Fuentevilla. 34/237 Fuentevilla 34/237 [11 3,741,563 June 26, 1973 3,410,109 11/1968 Maryland 62/457 3,056,440 10/1962 DeMello... 219/388 X 3,063,215 11/1962 Parks 53/388 2,216,884 10/1940 Kott 53/127 2,697,474 12/1954 McGinley 53/388 2,823,729 2/1958 Stickelber 53/388 3,599,394 8/1971 Vilen 53/388 3,570,391 3/1971 Rejler 99/443 C 1,641,313 9/1927 Bonaparte... 99/443C 3,491,679 1/1970 Kelly 99/443 C 3,516,218 6/1970 Eisler 53/25 FOREIGN PATENTS OR APPLICATIONS 1,221,727 1/1960 France 206/46 FR Primary Examiner-Granville Y. Custer, .Ir. Attorney-Davis, Hoxie, Faithful] & l-lapgood- [5 7] ABSTRACT large part of its surface, so that such part is accessible to a cooling medium.

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LENNABT hm! sTeusTmM D, u i, 3M m e APPARATUS FOR HEAT TREATING PACKAGED PRODUCTS 7 The present invention relates to apparatus for use in heat treating a product tightly enclosed in a flexible package, by subjecting it to a heat-inducing field such as an electro-magnetic or acoustic field. The apparatus is characterized by a supporting device for the package and comprising a number of flanges (including stubs or the like) arranged to lie close to the package and spaced a relatively short distance from each other, so that the package is prevented from being destroyed during the heat treatment due to a resulting pressure increase within the same, and the package over a large part of its surface is made accessible to a cooling medium without being removed from the supporting device.

Heat treatment of nutritional products in an electromagnetic or an acoustic field offers great advantages, as it can be accomplished very quickly. This is especially valuable, for example, in sterilization of nutritional products where discoloration, deterioration in taste, or other impairment in quality can occur if the product is maintained at too high a temperature for too long a time. In a so called micro-wave heat treatment, the generated thermal energy is distributed very quickly all through the product. This avoids the unfavorable distribution of temperature which results when the heating is accomplished in the conventional way, that is, a high temperature on the surface of the product and a low temperature in the interior of the product. For such volume heating, micro-waves are usually employed, but for special media with a large acoustic absorption and with a small dielectric dissipation factor, acoustic waves can be used instead.

However, there are many great problems hitherto unsolved in connection with micro-wave heating to a high temperature. When a product is heated, vapors are created, especially steam, and if the heat treatment takes place at temperatures considerably higher than 100 C., the vapor pressure in the product will be so high that the product can burst. In order to prevent this, the product must be surrounded by overpressure. Attempts have been made to heat-treat nutritional products in open packages and let these packages pass through a heat'treatment tunnel containing compressed air and- /or steam under pressure. Such a tunnel must be equipped with lock arrangements at both the entrance and the exit and must contain both a heating and a cooling section (possibly also a warm-keeping section), as the overpressure-around the products must be maintained until the products are cooled down. If not, the inner vaporpressure will burst the products. It is also a great problem that vapor from a heated product will be condensed on products not yet heat-treated or only partly cooled, or on the walls of the heat treatment equipment. Sterilization in an open package also has the great disadvantage that both the cooling of the product and the sealing of its package must be done aseptically.

The heat treatment of the products in an electromagnetic field can also be performed in closed packages. However, this creates other problems. The package material used in this case must be pressure-strong, cheap, and chemically resistant to the enclosed product at the applied treatment temperature. Packages of sheet metal cannot be used, however, as they do not pass electro-magnetic waves. They are reflected against the sheet, as is also the case for acoustic waves. Pressure-strong packages of glass or of a strong temperature-resistant plastic will be very expensive, as they must be made very stout in order to'resist the inner overpressure, and they are consequently only suitable for specific purposes, for example, pharmaceutical preparations. A thick-walled package has also the disadvantage that it makes a rapid cooling of the enclosed product impossible, whereby the product can lose in quality.

The present invention provides a cheap and umcomplicated solution of the problem discussed above, when using an electro-magnetic or acoustic field for heat treatment of nutritional products of different kinds.

According to the invention, the product is enclosed gas-tight and liquid-tight in a very thin packaging material, after which the package is placed in a supporting device provided with flanges (including stubs or the like) arranged to lie close to the package and at a relatively short distance from each other. During the following heat treatment, the package will be supported from the outside by the above-mentioned flanges and thereby prevented from bursting during the heating stage. The vapor which the product gives off remains in the package and contributes to an equalization of the differences in temperature, which can occur in the product. While the package is still supported by the flanges of the supporting device, it is thereafter cooled by a cooling medium, which will stream along the surface of the package. Due to the spacing of the supporting flanges from each other, a large part of the surface of the package will be accessible to the cooling medium. Thus, an extremely thin-walled package can be used, and it will be possible to cool the enclosed product very rapidly.

In a device according to the invention, products can be heat-treated in order to be sterilized. The heat treatment can also aim at an inactivation of enzymes in the product in order to make the taste of the product better or to interrupt a ripening process, for example, in cheese-making.

Products which can be heat-treated to advantage in an apparatus according to the invention are provisions or other nutritional products for man and animal; but also other products, such as nutrient substrata for micro cultures for production or research, can be treated in this way. The shape of the package is usually adapted to the product which is to be heat-treated. A package which is thin, flat and sealed along its edges is suitable for a product such as sliced ham, sliced cheese or the like. For other products, such as portions of mincedv or chopped meat, thicker packages will be more suitable. Other products can be placed in sealing boxes or cases or in packages with a bowl-shaped lower part and a flat lid. This lid can be provided on the inside with dotted or line-formed protuberances in order to prevent the enclosed product from contacting the lid to the detriment of its appearance. A loose network between the product and the lid can fulfill the same aim. For flowing or semi-rigid products, a package made up of long, hollow bands can be used, for example.

A suitable package material, for example, is a plastic with a sufficient thermal and chemical resistance. In certain cases laminated plastic is best. In especially difficult applications, the package may consist wholly or partly of thin glass or may be provided with an inset of thin glass.

For the heat treatment, a tunnel-arrangement can be used whereby the packaged products, in a device according to the invention, can be transported through a heating tunnel and thereafter be subjected to a cooling. By virtue of the invention, the products can also be subjected to heating and cooling alternately if that is desired. Even during the time when a product is treated with heat in an electro-magnetic way, the package can also be kept in contact with a heating or cooling medium. In order to preheat the products and/or heat the packing material and the device according to the invention, warm air or steam can stream through the tunnel or a part thereof.

The device according to the invention can be shaped in different ways. It can be shaped so that the supporting means form a tunnel-like space which is open at both its ends. The supporting means extend between the ends of the tunnel in the shape of flanges or a row of stubs or the like. Such an orientation of the supporting means facilitates inserting packages in and removing them from the device. By means of this orientation, channels for a cooling medium will be formed so that an efficient cooling is facilitated. Condensate on the inside of the upper part of the package or lid can be avoided or limited if the cooling medium, during the first part of the cooling course, is lead along the under side of the package and is able to cool it from below. The tunnel-like space for the package can be formed inside a box or a cylindrical casing.

The supporting device of the apparatus according to the invention can be arranged so that it forms a space having a shape fully corresponding to the product enclosed in the package, or it can be arranged so that it lies close to the package only at two sides. In the first mentioned case, at least one limiting wall of the space must be movable, for example, pivotably connected to another limiting wall, and it must be possible to keep it in this position for closing the space during the heat treatment, for example, by means of a spring lock device arranged to be closed and opened by hammer blows. In such an embodiment according to the invention, one or more of the above-mentioned limiting wall has openings through which a cooling medium can be led into and from the space for the package. In a preferred embodiment, the device according to the invention comprises a cylindrical casing having a removable end-wall and internal flanges including stubs or the like. The supporting means can be removably arranged in the casing in order to make the casing usable for different supporting means, which inshape and relative position suit differentkinds of packages. If the device according to the invention is shaped as a cylindrical casing, it will be strong and permanent in shape.

In the other case, that is, when the supporting means are arranged to lie close to the package from only two sides, the supporting means can be formed of two endless bands driven parallel to each other.

Some embodiments of the invention are further described in the following with reference to the accompanying drawings, in which FIGS. 1 and 2 are perspective views of two different embodiments and FIG. 3 is a schematic elevational view of a third embodiment.

In FIG. 1 there is shown a device formed as a casing l which is elongated and open at both ends. Internal flanges 2 extend between the open ends. Packages 4, enclosing products, are intended to be pushed into the casing through one opening 3 and to be removed through the other opening (not shown).

FIG. 2 shows a device shaped as a cylindrical casing 5 open at one end and provided with internal flanges 6. These flanges define a space 7 in which a product enclosed in a package can be placed. A wall 8 is arranged to close the open end of the casing 5 and is pivotably connected to the casing 5 and lockable to the same by locking means 9-9a. The movable end wall 8 and the opposite stationary end wall (not shown) are provided with openings through which a cooling medium can be led into and from the space 7.

A large number of devices according to FIG. 2 can be interconnected by connection means, as indicated at 5a, so that they form a closed chain which is movable, for example, in a horizontal track. In its circulation, each device at first passes a station where the product to be heat-treated is inserted in the space between the flanges 6 of the device, whereupon the end wall 8 is closed and locked by the locking means 9-9a. Thereafter, the device passes a heating station and then a cooling station and finally also a station where the above-mentioned end wall is lowered again. In order to discharge the treated product from the device, the latter is tilted a bit when it passes an unloading station. Many horizontal treatment tracks can be arranged at the side of or over each other.

FIG. 3 shows a device with supporting means comprising two bands 12 and 13 provided with flanges in the form of teeth 20 and driven parallel to each other. Packages 10 are fed in between the bands 12-13 by way of an inclined track 11. The two bands run around wheels 14-15 and 16-17, respectively. The wheels 15 and 16 are connected to a driving means (not shown). The bands are supported along a certain distance from either side by means of rolls 18. Further means can be arranged to function automatically to keep the bands together along this distance so that a sufficient support for the packages is obtained. On its way, each package passes a heating station (not shown) where the product enclosed in the package is heated. The package also passes a cooling section (not shown) where a cooling medium streams in between the flanges of the bands in order to cool the products in the packages 10 efficiently. When the heat treatment is finished, the packages are led away by another inclined track 19.

I claim:

1. In combination with a flexible package and a product tightly enclosed thereby and which, upon heating thereof, creates an internal pressure tending to rupture said package, a device for supporting said package for heat treatment in a heat-inducing field, said device comprising a plurality of rigid flanges spaced from each other and located to engage the exterior surface of said package from opposite sides of the package during the heat treatment, said device forming passages between said flanges for flow of a cooling medium, said flanges being positioned to expose said exterior surface over a large part thereof to said passages, whereby said flanges resist rupturing of the package while leaving said large part accessible to said cooling medium.

2. The combination according to claim 1, in which said device forms a tunnel-like space open at both ends.

3. The combination according to claim 2, in which said flanges extend between said ends of the tunnel-like space.

6 6. The combination according to claim 1, in which said device also comprises two endless bands carrying said flanges and adapted to be driven parallel to each other, said bands and their flanges being arranged to support the packages from said opposite sides. 

1. In combination with a flexible package and a product tightly enclosed thereby and which, upon heating thereof, creates an internal pressure tending to rupture said package, a device for supporting said package for heat treatment in a heat-inducing field, said device comprising a plurality of rigid flanges spaced from each other and located to engage the exterior surface of said package from opposite sides of the package during the heat treatment, said device forming passages between said flanges for flow of a cooling medium, said flanges being positioned to expose said exterior surface over a large part thereof to said passages, whereby said flanges resist rupturing of the package while leaving said large part accessible to said cooling medium.
 2. The combination according to claim 1, in which said device forms a tunnel-like space open at both ends.
 3. The combination according to claim 2, in which said flanges extend between said ends of the tunnel-like space.
 4. The combination according to claim 1, in which said device includes a cylindrical casing, said flanges being arranged within the casing.
 5. The combination according to claim 1, in which said device defines a space having essentially the form of said package and includes a movable wall partly defining said space.
 6. The combination according to claim 1, in which said device also comprises two endless bands carrying saId flanges and adapted to be driven parallel to each other, said bands and their flanges being arranged to support the packages from said opposite sides. 